Allow the GDT to be of any length #360
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Freax13
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Mar 27, 2022
phil-opp
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Mar 27, 2022
Signed-off-by: Joe Richey <joerichey@google.com>
Signed-off-by: Joe Richey <joerichey@google.com>
Freax13
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Mar 28, 2022
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| pub struct GlobalDescriptorTable<const MAX: usize = 8> { | ||
| table: [u64; MAX], | ||
| next_free: usize, | ||
| } |
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This is a bit too late, but I just noticed that this design allows creating GDT's without any entries, but a GDT must always have at least a null entry, doesn't it?
josephlr
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Mar 29, 2022
The GDT can have a maxium length of 2^16 bytes, and must contain at least one null descriptor. As `MAX` counts the number of `u64` entries, we must have `0 < MAX <= 2^13`. Unfortunely, we cannot do this check with a `where` clause, as `feature(generic_const_expers)` is not yet stable. However, we can do this check with an `assert!` in `GlobalDescriptorTable::empty()`, which is a `const fn`. Pointed out by @Freax13 in #360 (comment) Signed-off-by: Joe Richey <joerichey@google.com>
This was referenced Jan 14, 2024
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This uses a const generic
MAXparameter to specify the length. This is arguably a breaking change as it bumps the MSRV to 1.59 though its use of default const generics. It also can make some function call require additional type annotations:Fixes #333
Signed-off-by: Joe Richey joerichey@google.com